(a) Field of the Invention
The present invention relates to an electrostatic ink jet recording head and, more particularly, to an electrostatic ink jet recording head having an improved configuration of electrodes for ejecting toner particles to a recording medium.
(b) Description of the Related Art
Non-impact recording technique attracts special attention because of its remarkable low noise operation. Among other non-impact recording heads, an ink jet recording head has several advantages of high-speed recording, simple mechanism, direct recording onto a plain paper etc. Various mechanisms for the ink jet recording head have been proposed.
Examples of the ink jet recording head include an electrostatic ink jet recording head in which a voltage is applied between an opposite electrode installed in the rear side of a recording medium and a plurality of ejecting electrodes or recording electrodes of a head body opposed to the opposite electrode with the recording medium disposed therebetween. FIG. 1 shows a head body of this type of the conventional electrostatic ink jet recording head described in a Japanese Patent Application No. 07-120252 in a perspective view, and FIGS. 2A and 2B show detailed plan view and cross-sectional view, respectively, of the front edge portion of the head body of FIG. 1.
The head body of the ink jet recording head comprises an insulator substrate 31 made of glass, for example, on which a plurality of recording electrodes 32 are formed by sputtering of a metal such as chrome (Cr) and subsequent patterning thereof by using a photolithographic technology. The recording electrodes 32 are arranged in a 300 dpi (dot per inch) pitch, i.e., about 85 .mu.m pitch. The recording electrodes 32 are connected to a printing driver not shown in the drawings, and selectively applied therefrom with a high voltage pulse during a recording operation.
Meniscus elements 33 overlap the respective recording electrodes 32 except for the tip portion thereof for forming an ink meniscus in the vicinity of the recording electrodes 32. The meniscus elements 33 are made of a photosensitive polymer film laminated on the insulator substrate 31 and patterned by a photolithographic technology. Both the thickness and width of the meniscus elements 33 are about 30 .mu.m. A top cover plate 34 is disposed above the meniscus element 33, and the front edge of the cover plate 34 is slightly retreated from the tip of the meniscus elements 33. The top cover plate 34 is made of an insulator material and has an ink inlet port 35 and an ink outlet port 36 therein. The gap between the front edge portions of the insulator substrate 31 and the top cover plate 34 constitutes an ink jet slit 37, from which the meniscus elements 33 protrude together with the tips of the recording electrodes 32. The meniscus elements 33 extend backwards below the cover plate 34 for supporting the same. A side wall 40 extending along the side edges and rear edge of the head body is formed, together with the meniscus elements 33 during fabrication process, for defining an ink chamber together with the insulator substrate 31 and top cover plate 34.
The conventional electrostatic ink jet recording head as described above has a disadvantage in that it is expensive because of the complicated manufacturing process therefor, especially for the process for forming the meniscus elements 33. It also has a disadvantage in that the electrode structure is difficult to be arranged in a higher density.